Back support means

ABSTRACT

A back support mechanism (10) for a chair (9). The mechanism (10) has a pad (16) pivotally mounted to two links (17,18). An operating shaft (24) screw threadedly engages posts (19) mounted relative to guide rails (20). The links (17) cooperate with the posts whereby when the shaft (24) is rotated the posts (19) are caused to move along rails (20). This movement enables the pad (16) to pivot relative to the links (17) to cause the pad (16) to move out of the plane of the backrest (12) of the chair (9).

The invention relates to back support mechanisms.

Mass produced chairs and the like formed with a fixed back supportstructure do not provide adequate lumbar support for many users. Variousattempts have been made using selective padding of back rest zones inorder to provide comfort together with adequate lumbar support for avariety of users. Of course individual requirements vary to a date suchattempts have not been entirely successful. Also back rests have beenformed on adjustable mountings to vary the inclination thereof. However,such adjustment cannot accommodate variations in individual backconfigurations.

The present invention aims to alleviate the disadvantages associatedwith such prior art devices and to provide a back support mechanismwhich can be incorporated in backrests and which will be effective andefficient in use. It is also an object of this invention to provide sucha mechanism which can be adjusted to suit individual requirements.

With the foregoing and other objects in view, this invention provides aback support mechanism for a backrest of a chair including:

operating means;

adjustable support means mounted to the operating means;

control means for actuating said operating means to move said supportmeans out of the plane of the backrest for a chosen degree.

Preferably the adjustable support means bearing pad is movable in adirection substantially at right angles to the plane of the backrest. Ifdesired however, the bearing pad could be movable or pivotal foradjustment in any suitable manner so as to provide support in the lumbarregion of a user. In a preferred form the bearing pad is centrallydisposed and pivotally connected to the opposed supports arranged formovement towards or away from one another and the pivotal connectionbeing such that such movement causes a corresponding movement of thebearing pad substantially in the direction at right angles to the planeof movement of said supports. The supports can be adapted to movetransversely or in an up and down direction and of course if desired thebearing pad could be coupled to a single support or it could be locatedby other actuating mechanisms. Preferably the supports engage a threadedactuating shaft having external actuating means whereby rotation of theshaft will cause the supports to move together or away from one another.

The invention will now be described by way of example with reference tothe accompanying drawings in which:

FIG. 1 is a perspective view illustrating a typical application of thepresent invention;

FIG. 2 is a perspective view of a preferred form of back supportmechanism;

FIG. 3 is a plan view of the mechanism illustrated in FIG. 2;

FIG. 4 is a broken away view illustrating the operation of the backsupport mechanism;

FIG. 5 illustrates a modified mounting arrangement for the supportmechanism;

FIG. 6 illustrates another modified mounting arrangement for the supportmechanism; and

FIG. 7 shows a view illustrating the mode of adjustment of the mechanismof FIG. 6.

As illustrated the support mechanism 10 is adapted to be supportedbetween the side rails 11 of the backrest 12 of a chair. The side rails11 are upholstered and control means such as an operating knob 13 issupported in an accessible position projecting outwardly from thebackrest as illustrated in FIG. 1. The backrest 12 may include fixedupper and lower backrest panels 14 and an intermediate backrest panel 15which is separately upholstered and movable with respect to the adjacentpanels 14 such that adjustment of the panel 15 will not pull on thefixed upholstery fabric in the panels 14 and about the side rails 11 andcause creases and the like to form in the upholstery fabric.

The back support mechanism 10 includes adjustable support meanscomprising a central substantially rectangular bearing pad 16 which isconnected pivotally at opposite sides to laterally spaced link members17 each having upper and lower slotted arms 18 remote from the pad 16which engage about mountings or posts 19. Posts 19 are supportedslidably on upper and lower guide rails 20. The inner end portions 21 ofthe link members 17 extend inwardly beyond their pivotal connections 23with the bearing pad 16 and are formed with meshing projections 25.

The control means further includes a threaded shaft 24 having oppositehand threads at the respective end portions thereof extends between theside rails 11 and engages threadedly with the respective centralportions of the posts 19 such that upon rotation of shaft 24 the postsare both simultaneously moved either towards or away from one another,depending upon the direction of rotation of the shaft 24 along thesupporting rods 20. A control knob 13 is provided for rotating shaft 24.

In use, the back support mechanism is provided with suitable padding andis encased within suitable upholstery forming the intermediate section15.

A user supported in the chair 9 can by rotation of the knob 13 move thebearing pad 16 forwards or rearwards to provide the desired amount ofsupport at the lumbar region. When the control knob is rotated in onedirection the mounting posts 19 will move towards one another to causethe links 17 to pivot outwardly and carry the bearing pad 16 outwardlywith their inner ends to an outer position as illustrated in FIG. 4.Since both parts will move a corresponding amount the outer face of thebearing pad 16 is maintained in a parallel relationship with thesupporting plane of the backrest 12. If the knob 13 is rotated in theopposite direction the posts 19 will move apart enabling the links toretract towards the position illustrated in FIG. 2.

If desired return springs can be provided to cause retraction of thelinks 17, or the end parts on the slotted arms 19 could be adapted toencircle the respective post such that the links 17 would be drawn totheir retracted position. Alternatively the upholstery tension or theweight of a user may be used to cause retraction of the bearing pad 16.In the illustrated embodiment the meshing of the teeth 25 between theinner ends of the links 17 will ensure even retraction thereof.

FIG. 5 illustrates a modified mounting for the guide rails 20a wherebythe bearing pad 16a can be tilted about an axis coincident with theshaft 24. In this embodiment the ends of the guide rails 20a are locatedin sockets in respective side brackets 30 connected pivotally to amounting plate 31 screwed to the inside face of the respective siderails 11. The brackets (not shown) adjacent the control knob 13 pivotfreely about a bias on the mounting plate 31 while the opposite bracket30 is associated with a further control knob or lever on the outside ofthe side rails 11 such that it can be pivotal for indexed movementbetween a normal position, as illustrated and opposed inclinedpositions.

For this purpose a sleeve on the bracket 30 extends through an aperturein the plate 31 and the side rails 11. The inner end of the sleevesupports the bar 24 while the outer end supports the tilting control.Suitable indexing means may be provided and locking nut may be threadedabout the sleeve to hold the brackets 30 in their selected inclinationto selectively position the bearing pad 16a.

In the embodiment of FIGS. 6 and 7 the sleeve 50 which can be seen toform an axial extension of shaft 24 is spring biased by spring 40 to theright and is formed at a reduced diameter portion thereof with radialprojections 41. Each projection engages in a selected one of a pluralityof notches provided in the adjacent mounting plate 31. The outer end ofthe sleeve 50 has an operating knob 42 which may be manipulated bypressing it in the direction of the arrow A to cause it to compress thespring. This action disengages the radial projection from the notch.This action will enable relative rotation between side brackets 30 andplate 31. When the knob is released the projection may be located in adifferent one of the notches. In this fashion the angle at which thebearing pad projects out of the plane of the backrest may be varied. Inan alternative arrangement (not illustrated) a spline connection maybeprovided between the sleeve and the plate 31. By depressing the sleevein the manner mentioned above the sleeve may be rotated and relocated inthe plate 31 at a different angular position. In this way the angle atwhich the bearing pad projects from the backrest may be adjusted.

In an alternate form the control knob actuates a cam member which uponrotation bears against the back face of the bearing pad in a cammingaction to control its position. Also adjustable mounting means may beprovided to move the bearing pad in an up and down position to suit auser. Furthermore, the bearing pad could be supported by a scissors typelinkage or any suitable mechanical or electrical linkage or otherwise asdesired. The shaft 24 could be electrically driven and provided withremote control means.

The claims defining the invention are as follows:

I claim:
 1. A back support mechanism for a backrest of a chair mountablebetween two spaced side rails of a chair, said mechanismincluding:adjustable support means including laterally disposed linkmembers, each said link member having an upper and a lower arm, saidsupport means further including two guide posts, said arms of each saidlink member engaging with a respective said guide post at spacedlocations therealong, said arms being formed on an end portion of eachsaid link member, each said link member having meshing projectionsformed thereon and spaced from said arms such that said meshingprojections of said link members engage during operation of themechanism; a bearing pad means pivotally secured to said link membersadjacent said meshing projections and bridging between said linkmembers; a pair of spaced guide rails extending between the side railsof the chair, said guide posts being mounted for movement along theguide rails; and, control means including a screw threaded shaftengaging said guide posts such that rotation of said shaft in onedirection causes said guide posts to move towards one another andthereby cause the meshing projections to mesh and move the bearing padmeans to an extended position and rotation of said shaft in a directionopposite to said one direction causes said meshing projections to meshand said bearing pad means to move to a retracted position.
 2. Themechanism of claim 1, wherein said shaft has screw threaded portions ofopposite hand at respective end portions thereof, and each said screwthreaded portion engages with a respective said guide post to move theposts along the guide rails and thereby move the bearing pad meansbetween the extended and the retracted positions.
 3. The mechanism ofclaims 1 or 2, including tilting means for varying the angle at whichthe bearing pad means moves out of the plane of the backrest.
 4. Themechanism of claim 3, including biasing means for biasing the shaft inone axial direction and wherein said tilting means includes projectionsextending outwardly at one end of the shaft and notches formed in amounting means for said tilting means such that the shaft may be movedaxially against the biasing means to disengage the projections from thenotches to permit rotation of said support means and thereafter in saidone axial direction to re-engage the projections with the notches toenable the support means to project out of the plane of the backrest ata preselected angle.
 5. The mechanism of claims 1 or 2, including acontrol knob at both ends of the shaft whereby said shaft may be rotatedto operate the link members.
 6. The mechanism of claims 1 or 2,including a backrest panel mounted to said bearing pad means.
 7. Themechanism of claim 1, wherein said arms of each said link member areslotted and a respective said guide post is received in the slots insaid arms of a respective said link member.
 8. A chair in combinationwith the mechanism of claim 1.